The invention relates to an electronic system for operating an electromechanical parking brake device of a vehicle, with an input unit for detecting a driver command which is evaluated by a control unit which activates at least one actuating unit for actuating at least one brake.
An electromechanical parking brake device is known, inter alia, from DE 197 32 168 C1, and corresponding U.S. Pat. No. 6,394,235, both of which are incorporated by reference herein in entirety. A spindle/nut arrangement, which is actuated by an electric motor, serves as the actuating unit here, by means of which arrangement the brake piston of a brake of the service brake device can be mechanically locked.
An input unit for detecting a driver command for an electromechanical parking brake device is known from EP 1 128 999 B1. In this case the input unit is connected to an electronic control unit which directly converts the signals delivered by the input unit into corresponding activation signals for an actuating unit in order to change the parking brake device over to the desired actuating state.
According to EP 1 128 999 B1, in order also to enable the driver command relating to an actuation of the parking brake device, i.e. application or release, to be recognised and at the same time a fault diagnosis to be made in the event of a fault, the input unit must be constructed as a key or rocker key with a plurality of switch positions and deliver at least two redundant signals to the electronic control unit in each switch position.
This entails the disadvantage of having to connect a plurality of lines in parallel for the electrical connection between the input unit and the control unit. Thus, according to EP 1 128 999 B1, a total of eight lines, including the supply and earth lines, must be provided just for three switch positions and two redundant signals per switch position. This clearly illustrates the extent of the expenditure for the electrical connection between the input unit and the control unit, especially as reliable electrical contacting, e.g. a plug connection, has to be provided both on the input unit side and on the control unit side for each line.